Minor layout thread cleanups:

- lifetime naming
- unrequired reference removal
- containing_shadow_host getter simplification
- use stylist.device getter where possible

components/layout_thread/dom_wrapper.rs

@@ -175,20 +175,20 @@ pub struct ServoShadowRoot<'a> {
     chain: PhantomData<&'a ()>,
 }
 
-impl<'sr> Debug for ServoShadowRoot<'sr> {
+impl<'lr> Debug for ServoShadowRoot<'lr> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         self.as_node().fmt(f)
     }
 }
 
-impl<'sr> TShadowRoot for ServoShadowRoot<'sr> {
-    type ConcreteNode = ServoLayoutNode<'sr>;
+impl<'lr> TShadowRoot for ServoShadowRoot<'lr> {
+    type ConcreteNode = ServoLayoutNode<'lr>;
 
     fn as_node(&self) -> Self::ConcreteNode {
         ServoLayoutNode::from_layout_js(self.shadow_root.upcast())
     }
 
-    fn host(&self) -> ServoLayoutElement<'sr> {
+    fn host(&self) -> ServoLayoutElement<'lr> {
         ServoLayoutElement::from_layout_js(unsafe { self.shadow_root.get_host_for_layout() })
     }
 
@@ -205,8 +205,8 @@ impl<'sr> TShadowRoot for ServoShadowRoot<'sr> {
     }
 }
 
-impl<'sr> ServoShadowRoot<'sr> {
-    fn from_layout_js(shadow_root: LayoutDom<ShadowRoot>) -> ServoShadowRoot<'sr> {
+impl<'lr> ServoShadowRoot<'lr> {
+    fn from_layout_js(shadow_root: LayoutDom<ShadowRoot>) -> ServoShadowRoot<'lr> {
         ServoShadowRoot {
             shadow_root,
             chain: PhantomData,
@@ -220,8 +220,7 @@ impl<'sr> ServoShadowRoot<'sr> {
         guard: &SharedRwLockReadGuard,
     ) {
         unsafe {
-            &self
-                .shadow_root
+            self.shadow_root
                 .flush_stylesheets::<ServoLayoutElement>(device, quirks_mode, guard)
         };
     }
@@ -791,10 +790,7 @@ impl<'le> ::selectors::Element for ServoLayoutElement<'le> {
     }
 
     fn containing_shadow_host(&self) -> Option<Self> {
-        match self.containing_shadow() {
-            Some(shadow) => Some(shadow.host()),
-            None => None,
-        }
+        self.containing_shadow().map(|s| s.host())
     }
 
     fn prev_sibling_element(&self) -> Option<ServoLayoutElement<'le>> {

components/layout_thread/lib.rs

@@ -1351,10 +1351,13 @@ impl LayoutThread {
             document.shadow_roots().len()
         );
 
-        let device = Device::new(MediaType::screen(), initial_viewport, device_pixel_ratio);
         // Flush shadow roots stylesheets if dirty.
         for shadow_root in document.shadow_roots() {
-            shadow_root.flush_stylesheets(&device, document.quirks_mode(), guards.author.clone());
+            shadow_root.flush_stylesheets(
+                &self.stylist.device(),
+                document.quirks_mode(),
+                guards.author.clone(),
+            );
         }
 
         let restyles = document.drain_pending_restyles();